JPS5831310B2 - Method and apparatus for analyzing ink jet print head operation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for analyzing the operation of an ink jet printer head.

It is often desirable to analyze the operation of a device in order to properly operate the device and to indicate when errors have occurred in this operation.

Also, such devices are self-correcting in their operation.

That is, an indication that a malfunction has occurred is automatically processed by the device in order to make the necessary corrections.

Ensuring correct operation of a device is important in many cases, but particularly in ink jet print heads of ink jet printers.

In such printers, valves are opened to deliver ink from a pressurized source to an ink jet print head, resulting in an increase in pressure within the ink jet print head.

The speed of operation of the valve and the rate of pressure build-up within the ink jet print head are indicative of the operating condition of the valve and the ink jet print head.

If the valve is slow to operate, or if the valve does not open correctly, or if the pressure build-up in the ink jet print head is slow, proper operation will not occur and print quality will be significantly reduced. do.

Conventionally, various proposals have been made regarding the procedure for starting the operation of an ink jet print head (for example, US Pat. For example, U.S. Patent No. 3771568, U.S. Patent No. 3930258
No. 3,828,172, etc.), there has been no demonstration of automatically dynamically diagnosing the operation of ink jet print heads and recovering from malfunctions when they occur.

The present invention provides a method for monitoring and analyzing the operation of a device to detect the occurrence of a malfunction and, if this is correctable, to initiate a recovery process.

In particular, the present invention provides a method and apparatus for analyzing the operation of an ink jet print head, examining or detecting valve or pressure build-up malfunctions, and initiating recovery procedures if recovery thereof is possible. provide.

Accordingly, the main object of the present invention is to provide a method and apparatus for monitoring the operation of a device consisting of:

Another object of the present invention is to provide a method and apparatus for initiating a recovery procedure if a malfunction occurs and its recovery is possible.

Another object of the present invention is to provide a method and apparatus for analyzing the operation of an ink jet print head and using the same to check for malfunctions.

Another object of the present invention is to provide a method and apparatus for analyzing the operation of an ink jet print head by examining the time course between the start of operation and the time when the pressure builds up to a predetermined level. .

Another object of the invention is to provide a method and apparatus for analyzing the operation of an ink jet print head by examining the time course between the start of operation and the point in time when the pressure builds up to two different predetermined levels. That's true.

Another object of the present invention is a method and apparatus for determining the pressure characteristics of an ink jet print head and using this pressure characteristic to automatically initiate corrective action if this pressure characteristic indicates a malfunction. The goal is to provide the following.

Another object of the present invention is to provide an ink jet print head performance analysis apparatus that includes a counter, a comparator, and a microcomputer.

FIG. 1 shows an ink jet printer 7 having an ink jet print head 9. FIG.

Ink jet printers having such heads 9 are well known in the art, and therefore only those parts relevant to the present invention will be described in detail.

Head 9 is coupled via valve 13 to a pressurized ink source 11 .

Although the ink source is described as being pressurized, a separate pressure source may be provided.

What is required in this case is a pressure build-up or rise when there is ink in the head, so that the ink is transferred from the ink jet print head to the paper 15 as in a conventional ink jet printer.
It is resistant to wear.

Valve 13 is preferably an electromagnetic valve controlled by valve control device 17 via valve drive device 19 .

As is well known, such a valve can be opened by an electrical output signal applied via a valve driver 19 from a valve control unit.

As shown in FIG. 1, electrical output signals from valve control unit 17 are also coupled to sensing system 21.

The ink jet print head 9 has a pressure response transducer 23 for sensing pressure build-up within the head.

The transducer 23 is preferably a piezoelectric crystal and is used in an inkjet system to transform the ink stream into ink droplets.
Preferably, it is the same crystal used to energize the print head.

The output from the piezoelectric crystal or transducer 23 is an electrical signal proportional to the increase in pressure compressing the piezoelectric crystal within the head.

This signal is coupled to sensing system 21.

The period during which the pressure within the head gradually increases is the pressure change period.

In the sensing system 21 the time for the pressure to reach the predetermined level is measured and an output signal representing this time is sent to a microcomputer for analysis of the operation of the head and valve mechanism.

The time between the start time of operation determined by the generation of the output signal from valve control unit 17 and the actual start time of the build-up of pressure within the ink jet print head is indicative of the general operating characteristics of this valve mechanism.

If the start time falls outside the allowable value, the microcomputer 25 lights up the console display lamp 24 to indicate that the valve mechanism needs to be inspected.

Also, by determining the length of time it takes for the pressure to reach an operating value, the ink flow can be properly ejected from the ink jet print head onto the media. - Check the condition of the jet print head.

Depending on the pressure build-up or rise time, the microcomputer 25 energizes the print controller 26 to initiate a printing operation or to initiate a self-healing or clean amplifier procedure for the head.

The print control device 26 controls functions necessary for printing.

These functions are: control of the relative movement between the ink jet print head and print media, data synchronization and deflection for the ink drops, and self-healing operation for the head 9.

FIG. 2 shows in block diagram form the sensing system 21 of the present invention.

The first input to gate 29 is an electrical signal from valve control unit 17.

The second input to gate 29 is the clock input from clock 31, which operates at an arbitrary clock frequency (eg 16MH2).

A signal for opening the valve 13 is sent to the valve control unit 17
When applied to valve 13, this signal is also applied to gate 29, which gates the clock signal.

The output from gate 29 is connected to a delay counter 33 and when the output signal is gated by gate 29, the delay counter begins counting at a rate controlled by the frequency of the clock input to gate 29.

The ink passes through the valve 13 to the ink jet.
As the ink jet print head is fed to print head 9, the pressure within the ink jet print head begins to increase.

An increase in pressure within the head causes the piezoelectric crystal to distort, producing an electrical output signal (which may be amplified) with an amplitude proportional to this pressure.

The piezoelectric crystal 23 has sufficient frequency response characteristics to sense the pressure rise time to be sensed.

Examples of this rise time are discussed below with respect to FIGS. 3, 4, and 5.

Alternatively, a DC pressure transducer can be placed within the ink jet cavity of the head 9, separate from the piezoelectric crystal 23, to provide a pressure signal to the sensing system 21.

Since the piezoelectric crystal 23 also acts as a driving crystal for ink drop generation in the ink jet print head, the crystal 23 can operate the crystal in two different modes of operation: It is connected to a switch 35 for switching the crystal between a drive mode and a mode that senses pressure build-up within the ink jet print head.

Switching of this switch 35 is performed by a mode control input signal.

When switch 35 is in the sensing mode position as shown in FIG.
9 and 41 are connected to one input each.

This input to these comparators is
Indicates the amount of pressure build-up within the print head.

Applied to the second input of comparator 39 is a reference signal or voltage that indicates the beginning of a pressure build-up within the ink jet print head.

As the pressure begins to rise in the head, the signal connected from the piezoelectric crystal 23 to the comparator 39 increases.

If this signal level exceeds the reference level, the comparator 39
produces an output signal, which is sent to the delay counter 33 to stop the counting operation of this counter 33 there.

This counting operation is performed from the valve control unit 17 to the gate 2.
9 is started by a signal indicating the start of operation.

The output signal of the comparator 39 is also applied to one of the gates 43.

Gate 43 converts the clock signal from clock 31 into a second clock signal.
A clock signal is applied via gate 43 to rise time counter 45 when an output signal is received from comparator 39 representing the beginning of a rise in pressure within the ink jet print head. The counter 45 then starts counting at a rate determined by the frequency of the clock signal.

An input signal representative of the pressure within the piezoelectric crystal 23 is also applied to a comparison device 41.

Comparator 41 also receives a second reference level signal or voltage as a second power source.

This second reference level is greater than the first reference level to comparator 39 and approximately equal to the ink drop supply or operating level in the head.

When the pressure within the ink jet print head exceeds a second reference level, comparator 41 produces an output signal which is applied to rise time counter 45 to cause its counting operation to occur at that point. Stop.

The counted value of the delay counter 33 is sent to the delay register 53 of the memory 55 in the microcomputer 25 via the logic gate 49 and the data bus 51.

This microcomputer 25 also includes a microprocessor 57.

This count value is stored in the delay register 53 and used to calculate the elapsed time between the switching time of the valve control unit 17 and the start time of the pressure increase in the head.

Similarly, the count value of the rise time counter 45 is
It is sent via logic gate 59 and data bus 51 to rise time register 61 of memory 55 of microcomputer 25.

This count represents the rate of pulse rise, or pressure rise time within the ink jet print head.

As shown in FIG. 2, the transfer of counts from counters 33 and 45 is controlled by address decoding unit 63.

When microprocessor 57 generates an address for delay register 53, address decoding unit 63 generates an enable signal to logic gate 49.

Microprocessor 57 causes rise time register 61
When generating an address for , address decoding unit 63 generates an enable signal to logic gate 59 .

When activated, logic gates 49 and 59 transfer the counts in delay counter 33 and rise time counter 45 to registers 53 and 61, respectively.

After transferring the counts of delay counter 33 and rise time counter 45 to the memory registers of microcomputer 25, this data is used to perform the necessary calculations, decisions and recording.

The count data can be used, for example, to update statistics in a microprocessor diagnostic log that relate to the frequency of valve start indication counts to generate a frequency distribution for the start rate.

This data, used in conjunction with the microprocessor generating statistics regarding valve operating trends, can also be used to indicate the impending occurrence of hend and valve failure, thus prompting the printer to This is useful in terms of maintenance.

FIG. 3 is a system diagram showing the operation of the microprocessor 57.

As shown, a determination is first made at decision block 100 as to whether the data from delay register 53 is equal to or greater than the value X1.

Here, Xl is the lower limit time for drawing the valve, and is, for example, 3 msec.

If the answer is no, action block 101
The following actions are performed.

In other words, a light (
An output signal is generated, for example for energizing lamp 24) in FIG.

At the same time, the valve pick number and delay are set to operation block 10.
2 may be stored in memory 55.

If the data in delay register 53 is greater than value X1 and is equal to or greater than value X2 (decision block 103, where value X2 is the upper limit time for retracting the valve, e.g. ), the operation of operation block 101 described above is performed.

If the data in delay register 53 is equal to or greater than value X1 and less than value X2, data is retrieved from rise time register 61 in operation block 104.

The microprocessor also retrieves the rise time data when valve maintenance is indicated.

If the rise time is within limits, the printing operation can proceed even if the valve operation is outside the acceptable range.

Next, the frequency distribution of rise times is updated.

Next, in decision block 106, it is determined whether the rise time is equal to or greater than the value X3, and if the answer is yes, action block 107
A device self-recovery procedure is performed at , and the start-up procedure is automatically repeated at action block 108 .

The above value X3 is the upper limit value of the rise time, and is, for example, 5 msec.

If the rise time is less than the value X3, and the value
If it is less than 4 (eg, 2 msec) (decision block 109), the printer is commanded to deliver ink to the paper, thus starting the printing operation.

If the rise time is greater than or equal to the value X4 and less than the value X3, it indicates the presence of air in the head, and the start of the printer operation is delayed by the value Z, after which the printing operation begins. begins.

Here, the value Z is the delay time required to remove air from the ink within the ink jet print head.

Referring to FIG. 4, three examples of leading edges of pulses originating from piezoelectric crystal 23 are shown.

The start time t1 and rise time t2 of the three waveforms A, B, and C are marked with corresponding appended letters A, B, and C, respectively.

Waveform A shows a normal start-up condition indicating that the valve is operating within tolerance and the pressure rise time t2A is adequate for ink jet generation.

Waveform B shows an example where the valve activation is within the tolerance range but the pressure rise is abnormally low.

A phenomenon caused by the low pressure rise is that ink is scattered and stuck to other components of this head.

Therefore, in this case, the printing operation is not performed correctly and a recovery procedure is initiated.

Waveform C shows an example in which the start time is delayed because the state in which the valve is energized is outside the allowable error range, but the pressure rises normally after it is started.

In this case, normal printing operation is expected, but it is necessary to check the valve because there is a risk of failure later.

The following diagnostic table shows the values XI, X
2. The criteria for selecting X3 and X4 are shown below.

When the start time is less than the value X1 or equal to or greater than the value X2, the operation of the valve is outside the tolerance range and there is a high probability of future valve failure.

A rise time less than the value X1 may be caused by the valve being out of tolerance or by the valve being energized too briefly during the stroke of switching the ink flow on and off.

A start time equal to or greater than the value X2 indicates that the operation of the valve mechanism is slow, probably due to contamination thereof.

This also indicates that the force of the drive signal energizing the valve solenoid is weak, or that the solenoid itself is weak.

Waveform C in FIG. 4 is an example where the start time is greater than the value X2.

A rise time t2 equal to or greater than the value X3 indicates that the pressure rises too slowly.

A possible cause in this case is that the ink jet print head assembly is wetted by the ink jet.

Other possible causes include the presence of excess air in the ink cavity of the head or a malfunction in the pressure system that pressurizes the ink.

Waveform B in FIG. 4 shows an example where the rise time is greater than the value X3.

A rise time equal to or greater than the value X4 but less than the value X3 means that the pressure rise in the head is slow, but this slow rise is slow enough to cause wetting of the head during the start of operation. It means that there is no.

This indicates that although control of the ink jet flow is difficult, the printing operation will likely be successful.

One possible cause of slower than normal rise time is the presence of air within the head.

By delaying the start of the printing operation by a certain amount of time, this air dissolves into the ink and is no longer present.

Another cause of slow rise time is lower ink pressure.

In this case, controlling the ink flow is difficult.

If the rise time t2 is smaller than the value X4, the pressure rise within the head is normal and good printing operation can be expected.

Waveforms A and C are examples when the rise time is appropriate.

Although examples have been described where the start time and rise time are somewhat short, the allowable rise time and allowable start time will vary depending on the ink jet printing system used.

The values X1, X2, X3 and X4 can be easily changed by reprogramming the microprocessor.

These values may vary depending on the ink jet assembly to which the invention is applied.

Thus, a high count in register 53 can be used to indicate the need for valve maintenance, while a high count in distalo 1 leaves the system unprepared to dissolve trapped air bubbles. This ensures proper ink droplet generation operation.

High count values can also be used to initiate individual level self-healing, such as expelling air from the head, restarting the valve, or cleaning the deflection electrode.

Although the invention has been described in terms of pressure build-up, the invention is also applicable to measuring the rate of pressure decay within an ink jet print head after a valve is closed.

Such pressure decay characteristics may also be used to determine whether ink jet print heads and associated valve mechanisms are operating properly.

The present invention automatically and dynamically analyzes the operation of devices, such as ink jet print heads, and detects, for example, valve malfunctions, air entrapment during valve cycles, defects after head replacement. Complete expulsion of air or pressure leakage in the ink system can be detected.

[Brief explanation of the drawing]

FIG. 1 is a block system diagram showing an ink jet printing system incorporating the analysis device of the present invention, and FIG. 2 is a block system diagram showing the analysis device of the invention. FIG. 3 is a system diagram showing the operation of the microprocessor shown in FIG. 2. FIG. 4 is a chart showing examples of pressure waveforms that can be analyzed by the present invention. 11... Ink source, 13... Valve,
9...Herad, 23...Piezoelectric crystal, 1
5...paper, 21...sensing system,
25...Microprocessor, 19...
・Valve drive device, 17... Valve control unit, 31... Clock, 29, 43...
・Gate, 49, 59...Logic gate, 33・
... Delay counter, 45 ... Rise time counter, 39°41 ... Comparison device, 37
7 drive unit, 57 microprocessor, 61 rise time register, 53 delay register, 51...
Data bus, 63...address decoding unit.

Claims (1)

[Scope of Claims] 1. A method for analyzing the operation of an ink jet print head that ejects ink based on internal pressure, comprising: 2. Within the ink jet print head during a period of predetermined pressure change. sensing a pressure characteristic of the ink jet print head, determining a pressure build-up condition within the ink jet print head during the pressure change period based on the sensed pressure characteristic;
The above-mentioned ink jet printing apparatus is characterized in that the deviation of the operation of the print head from a normal state is detected.
How to analyze head behavior. 2. A device for analyzing the operation of an ink jet print head that ejects ink based on internal pressure, which senses the pressure inside the ink jet print head and generates an electrical output proportional to the sensed pressure. a pressure responsive transducer disposed within the ink jet print head for generating a signal and the ink jet print head during a period of predetermined pressure changes in the ink jet print head; an apparatus responsive to the electrical output signal for determining a rise time of a pressure within the ink jet print head and detecting a deviation from a normal state of operation of the ink jet print head based on the rise time. A device for analyzing the operation of the above-mentioned inkjet print head. 3. The means responsive to the electrical output signal comprises a time measuring device for determining the time from the start of operation until the pressure in the ink jet print head reaches a predetermined pressure level. An apparatus for analyzing the operation of an ink jet print head as claimed in claim 2. 4. The time measuring device includes a counter that starts counting at the start of operation, and a counter that stops counting when the pressure inside the ink jet print head reaches the predetermined pressure level. An ink jet apparatus according to claim 3, further comprising a device for comparing said electrical output signal with a reference signal.
A device that analyzes print head operation. 5 Means responsive to the electrical output signal compares the electrical output signal and a first reference level signal and determines the first reference level signal when the electrical output signal exceeds the first reference level signal.
a first comparator for generating an output signal; a second comparator for comparing the electrical output signal and a second reference level signal and producing a second output signal when the electrical output signal exceeds the second reference level signal; 2 comparators, a first counter connected to the first comparator for counting the period between the start of the pressure supply operation and the occurrence of the first output signal;
a second counter connected to the first and second comparison devices for counting the period between the time of occurrence of the output signal and the time of occurrence of the second output signal; Claims further comprising means connected to said first and second counters for initiating an indicating or corrective action when indicating a deviation from a normal state of operation of the ink jet print head. An apparatus for analyzing the operation of an ink jet print head according to claim 2.